Noncrossing Matchings with Fixed Points

Weiming Weng1, Bolian Liu2
1Department of Computer Science, Guangdong Polytechnic Normal University Guangzhou 510665, P. R. China,
2School of Mathematical Sciences, South China Normal University Guangzhou 510631, P. R. China

Abstract

The noncrossing matchings with each of their blocks containing a given element are introduced and studied. The enumeration of these matchings is described through a polynomial of several variables, which is proved to satisfy a recursive formula. Results of the enumeration of noncrossing matchings with fixed points are connected with Catalan numbers.